Hot maceration

The raw material is dried or wilted to reduce its water, because any water left will make the oil go rancid quickly.

The material is fully submerged in carrier oil and kept warm, usually in a water bath or in the sun.

After hours to days, the spent material is filtered out. The process can be repeated with fresh material to raise the concentration.

The final product is an oil that has absorbed the fragrance, used directly without further dilution.

It gives a rounder, warmer smell than the fresh material, because the moderate temperature gently changes some components without destroying them. This method gives the product closest to what you perceive in the kitchen.

The product is a diluted oil, not an essential oil, so it cannot be compared directly for concentration. Heat also destroys some fragile molecules, although far more gently than distillation.

The product is always greasy and always carries the smell of the carrier oil beneath the fragrance. If a bottle says pure essential oil but a drop on paper leaves an oily mark that does not evaporate after many hours, it is most likely a macerated oil rather than an essential oil.

Maceration in oil is the oldest and most widespread method in the world before distillation. The Egyptians, Greeks and Romans all used olive oil as a base to hold the scent of flowers and spices.

In Vietnam the technique has never disappeared. The ginger, turmeric and lemongrass oils of folk medicine are all products of hot maceration, and the way many families make them today hardly differs from how it was done two thousand years ago.